Composition for window film, flexible window film formed therefrom, and flexible display device comprising same

ABSTRACT

Provided are: a composition for a window film; a flexible window film formed therefrom; and a flexible display device comprising the same, wherein the composition contains: a siloxane resin comprising chemical Chemical Formula 1 or 2 or a mixture thereof; a cross-linking agent; and an initiator, the cross-linking agent being contained in a content of about 10-30 parts by weight on the basis of 100 parts by weight of the siloxane resin or the mixture thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Patent Application and claimspriority to and the benefit of International Application NumberPCT/KR2015/013827, filed on Dec. 16, 2015, which claims priority to andthe benefit of Korean Application No. 10-2014-0182744, filed on Dec. 17,2014, the entire contents of each of which are incorporated herein byreference.

BACKGROUND 1. Field

The present invention relates to a composition for window films, aflexible window film produced therefrom, and a flexible displaycomprising the same.

2. Description of the Related Art

Recently, a flexible display capable of being folded or unfolded hasbeen developed in the related art. The flexible display is thin andlight, has high impact resistance, can be folded and unfolded, and thuscan be manufactured in various shapes.

In such a flexible display, not only a substrate but also variouselements are required to have flexibility. Particularly, since a windowfilm is disposed at the outermost side of the display, it is necessaryfor the window film to have flexibility, high hardness and opticalreliability. Further, since the window film is manufactured by coatingand curing a composition for window films on a base layer, the windowfilm can suffer from curling.

SUMMARY

It is one aspect of the present invention to provide a composition forwindow films, which can realize a flexible window film capable ofsuppressing curling.

It is another aspect of the present invention to provide a compositionfor window films, which can realize a flexible window film having goodproperties in terms of hardness, flexibility and optical reliabilitysuch as light resistant reliability.

It is a further aspect of the present invention to provide a flexiblewindow film, which can suppress curling and has good properties in termsof hardness, flexibility and optical reliability such as light resistantreliability, and a flexible display including the same.

In accordance with one aspect of the present invention, a compositionfor window films includes: a siloxane resin represented by ChemicalFormula 1 or a siloxane resin represented by Chemical Formula 2 or amixture thereof; a crosslinking agent; and an initiator, thecrosslinking agent is present in an amount of about 10 parts by weightto about 30 parts by weight relative to 100 parts by weight of thesiloxane resin or the mixture thereof:

(R¹SiO_(3/2))_(x)(R²SiO_(3/2))_(y)  <Chemical Formula 1>

(wherein Chemical Formula 1, R₁ and R₂ are the same as defined in thefollowing detailed description; and 0<x≦1, 0≦y<1, and x+y=1),

(R¹SiO_(3/2))_(x)(R³R⁴SiO_(2/2))_(z)(R²SiO_(3/2))_(y)  <Chemical Formula2>

(wherein Chemical Formula 2, R¹, R², R³ and R⁴ are the same as definedin the following detailed description; and 0<x<1, 0<y<1, 0<z<1, andx+y+z=1).

In accordance with another aspect of the present invention, a flexiblewindow film includes: a base layer and a coating layer formed on onesurface of the base layer, wherein the flexible window film has acurling of about 1.0 mm or less and the coating layer is formed of thecomposition for window films as set forth above.

In accordance with a further aspect of the present invention, a flexibledisplay includes the flexible window film as set forth above.

The present invention provides a composition for window films, which canrealize a flexible window film capable of suppressing curling.

The present invention provides a composition for window films, which canrealize a flexible window film having good properties in terms ofhardness, flexibility and optical reliability such as light resistantreliability.

The present invention provides a flexible window film, which cansuppress curling and has good properties in terms of hardness,flexibility and optical reliability such as light resistant reliability,and a flexible display including the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a flexible window film according toone embodiment of the present invention.

FIG. 2 is a cross-sectional view of a flexible window film according toanother embodiment of the present invention.

FIG. 3 is a cross-sectional view of a flexible display according to oneembodiment of the present invention.

FIG. 4 is a cross-sectional view of one embodiment of a display partshown in FIG. 3.

FIG. 5 is a cross-sectional view of a flexible display according toanother embodiment of the present invention.

FIG. 6 is a cross-sectional view of a flexible display according to afurther embodiment of the present invention.

FIG. 7 is a diagram illustrating a method of measuring a curling.

DETAILED DESCRIPTION

Embodiments of the present invention will be described in detail withreference to the accompanying drawings. It should be understood that thepresent invention is not limited to the following embodiments and may beembodied in different ways. In the drawings, portions irrelevant to thedescription will be omitted for clarity. Like components will be denotedby like reference numerals throughout the specification.

Herein, spatially relative terms such as “upper” and “lower” are definedwith reference to the accompanying drawings. Thus, it will be understoodthat the term “upper surface” can be used interchangeably with the term“lower surface”. In addition, when an element such as a layer or a filmis referred to as being placed “on” another element, it can be directlyplaced on the other element, or intervening element(s) may be present.On the other hand, when an element is referred to as being placed“directly on” another element, there are no intervening element(s)therebetween.

Herein, the term “pencil hardness” is measured on a coating layer of awindow film using a pencil hardness tester (Heidon) in accordance withJIS K5400. In measurement of pencil hardness, pencils of 6B to 9H(Mitsubishi Co., Ltd.) are used. Specifically, pencil hardness ismeasured under conditions of a pencil load of 1 kg on the coating layer,a scratch angle of 45°, and a scratch speed of 60 mm/m in. When thecoating layer has one or more scratches after being tested 5 times usinga certain pencil, pencil hardness is measured again using another pencilhaving one-level lower pencil hardness than the previous pencil, and themaximum value of pencil hardness allowing no scratch to be observed allfive times on the coating layer is taken as pencil hardness of thecoating layer.

Herein, the term “radius of curvature” refers to a minimum radius of ajig causing no cracks on a window film specimen when the window filmspecimen is wound around the jig for measuring a radius of curvature(CFT-200R, COVOTECH Co., Ltd.), kept wound for 5 seconds, unwound, andthen observed with the naked eye to determine whether the specimen hascracks. Here, a radius of curvature in a compressive direction ismeasured when the specimen is wound around the jig such that a windowcoating layer of the window film contacts a surface of the jig, and aradius of curvature in a tensile direction is measured when the specimenis wound around the jig such that a base layer of the window filmcontacts the jig. Here, the window film specimen has a thickness of 50μm to 300 μm.

Herein, the term “ΔY.I.” refers to a difference (Y2−Y1) between a yellowindex (Y1) measured on a window film under a D65 light source at 2°(angle between the window film and the light source) using a colorimeter(CM3600D, Konica Minolta) and a yellow index (Y2) measured on the windowfilm by the same method after irradiating the window film at a peakwavelength of 306 nm for 72 hours using a light resistance tester(CT-UVT, Core Technology Inc.).

Herein, referring to FIG. 7, the term “curl” means average value of amaximum height (H) from a floor (2) to a window film (1) placed on thefloor (2) such that a base layer of the window film (2) contacts thefloor, as measured after the window film (1) is left under conditions of22° C. to 28° C. and 30% relative humidity to 50% relative humidity.

Herein, the term “(meth)acryl” refers to acryl and/or methacryl. Herein,unless otherwise stated, “substituted” means that at least one hydrogenatom in a functional group is substituted with a hydroxyl group, anunsubstituted C₁ to C₁₀ alkyl group, a C₁ to C₁₀ alkoxy group, a C₃ toC₁₀ cycloalkyl group, a C₆ to C₂₀ aryl group, a C₇ to C₂₀ arylalkylgroup, a benzophenone group, a C₆ to C₂₀ aryl group substituted with aC₁ to C₁₀ alkyl group, or a C₁ to C₁₀ alkyl group substituted with a C₁to C₁₀ alkoxy group.

Herein, the term “crosslinkable functional group” means a functionalgroup allowing crosslinking reaction by heat and/or light. For example,the crosslinkable functional group means an epoxy group, an epoxygroup-containing group, a glycidyl group, a glycidyl group-containinggroup, a glycidoxy group, a glycidoxy group-containing group, anoxetanyl group, an oxetanyl group-containing group, and the like.Specifically, the crosslinkable functional group means an epoxy group; aglycidyl group; a glycidoxy group; an oxetanyl group; an oxetanyloxygroup; an epoxy group, a glycidyl group, a glycidoxy group, anepoxylated C₅ to C₂₀ cycloalkyl group, an epoxylated C₁ to C₁₀ alkylgroup, an oxetanyl group or an oxetanyloxy group-containing C₁ to C₂₀alkyl group; or an epoxy group, a glycidyl group, a glycidoxy group, anepoxylated C₅ to C₂₀ cycloalkyl group, an epoxylated C₁ to C₁₀ alkylgroup, or an oxetanyl group or oxetanyloxy group-containing C₅ to C₂₀cycloalkyl group, and may be unsubstituted or substituted with anotherelement. Herein, the term “UV absorption functional group” means afunctional group capable of absorbing light at a wavelength of about 400nm or less, for example, about 100 nm to about 400 nm. Specifically, theUV absorption functional group may include an unsubstituted orsubstituted benzotriazole group, an unsubstituted or substitutedbenzophenone group, an unsubstituted or substituted hydroxybenzophenonegroup, an unsubstituted or substituted triazine group, an unsubstitutedor substituted salicylate group, an unsubstituted or substitutedcyanoacrylate group, an unsubstituted or substituted oxanilide group, anunsubstituted or substituted hydroxyphenyltriazine group, anunsubstituted or substituted hydroxyphenylbenzotriazole group, or anunsubstituted or substituted hydroxyphenylbenzophenone group, withoutbeing limited thereto.

Herein, the term “UV absorption functional group-containing group” meansa group containing the UV absorption functional group. Herein, the term“alkyleneoxy group” means an alkylene group having oxygen (O) at aterminal or inner structure thereof. Herein, the term “halogen” meansfluorine, chlorine, bromine, or iodine. Herein, “Ec” refers to a(3,4-epoxycyclohexyl)ethyl group, “Gp” refers to a 3-glycidoxypropylgroup, “Op” refers to a 3-oxetanylpropyl group, and “Me” refers to amethyl group.

Hereinafter, a composition for window films according to one embodimentof the present invention will be described.

The composition for window films according to the embodiment includes: asiloxane resin comprising a compound represented by Chemical Formula 1or Chemical Formula 2 or a mixture thereof, a crosslinking agent and aninitiator, the crosslinking agent is present in an amount of about 10parts by weight to about 30 parts by weight relative to 100 parts byweight of the siloxane resin or the mixture thereof:

(R¹SiO_(3/2))_(x)(R²SiO_(3/2))_(y)  <Chemical Formula 1>

(wherein Chemical Formula 1, R¹ is a crosslinkable functional group; R²is a UV absorption functional group or a UV absorption functionalgroup-containing group; and 0<x≦1, 0≦y<1, and x+y=1),

(R¹SiO_(3/2))_(x)(R³R⁴SiO_(2/2))_(z)(R²SiO_(3/2))_(y)  <Chemical Formula2>

(wherein Chemical Formula 2, R¹ is a crosslinkable functional group; R²is a UV absorption functional group or a UV absorption functionalgroup-containing group; R³ and R⁴ are each independently hydrogen, acrosslinkable functional group, an unsubstituted or substituted C₁ toC₂₀ alkyl group, or an unsubstituted or substituted C₅ to C₂₀ cycloalkylgroup, at least one of R³ and R⁴ being an unsubstituted or substitutedC₁ to C₂₀ alkyl group; and 0<x<1, 0<y<1, 0<z<1, and x+y+z=1).

With the siloxane resin comprising the compound represented by ChemicalFormula 1 or Chemical Formula 2 or the mixture thereof, the compositionfor window films according to the embodiment can improve hardness,flexibility and optical reliability, such as light resistantreliability, of a window film formed of the same. In addition, thesiloxane resin is prepared through adjustment of the content of eachsilicon monomer, thereby allowing easy adjustment of hardness,flexibility and optical reliability, such as light resistantreliability, of the window film. Specifically, in one embodiment, inChemical Formula 1, 0.20≦x≦0.999, 0.001≦y≦0.80, more specifically0.20≦x≦0.99, 0.01≦y≦0.80, still more specifically 0.80≦x≦0.99,0.01≦y≦0.20. In another embodiment, Chemical Formula 1 may berepresented by (R^(1a)SiO_(3/2))_(x1)(R^(1b)SiO_(3/2))_(x2) (R^(1a) andR^(1b) are different crosslinkable functional groups, 0<x1<1, 0<x2<1,and x1+x2=1), specifically 0.70≦x1<1 and 0<x2≦0.30, specifically0.80≦x1<1 and 0<x2≦0.20, more specifically 0.85≦x1≦0.99 and0.01≦x2≦0.15. In Chemical Formula 2, 0.40≦x≦0.99, 0.001≦y≦0.20,0.001≦z≦0.40, more specifically 0.80≦x≦0.98, 0.001≦y)≦0.10, and0.005≦z≦0.10, still more specifically 0.80≦x≦0.98, 0.01≦y≦0.10, and0.01≦z≦0.10. Within this range, the siloxane resin can improve hardness,flexibility and light resistant reliability of the window film.

In Chemical Formula 1, R¹ can provide crosslinkability to thecomposition for window films. Specifically, R¹ may be a(3,4-epoxycyclohexyl)methyl group, a (3,4-epoxycyclohexyl)ethyl group, a(3,4-epoxycyclohexyl)propyl group, a 3-glycidoxypropyl group, a3-oxetanylmethyl group, a 3-oxetanylethyl group, a 3-oxetanylpropylgroup, or a 3-oxetanyloxy group. R² can absorb UV light. Specifically,R² may be an unsubstituted or substituted hydroxybenzophenone group, anunsubstituted or substituted hydroxyphenyltriazine group, or a grouprepresented by Chemical Formula 3.

*—(R^(x))_(n1)-M-(R^(x))_(n2)—R^(y)  <Chemical Formula 3>

(wherein Chemical Formula 3, * is a linking site with respect to Si;R^(x) is an unsubstituted or substituted C₁ to C₂₀ alkylene group, anunsubstituted or substituted C₁ to C₂₀ alkyleneoxy group, anunsubstituted or substituted C₁ to C₂₀ alkylene group having a urethanegroup at a terminal or inner structure thereof, an unsubstituted orsubstituted C₁ to C₂₀ alkyleneoxy group having a urethane group at aterminal or inner structure thereof, an unsubstituted or substituted C₆to C₂₀ arylene group, or a combination thereof, n1 and n2 are eachindependently 0 or 1, M is a single bond, oxygen (O), sulfur (S), NR (Rbeing hydrogen or a C₁ to C₁₀ alkyl group), —CONH—, —OCONH—, —C═O—, or—C═S—, and R^(y) is an unsubstituted or substituted benzotriazol group,an unsubstituted or substituted benzophenone group, an unsubstituted orsubstituted hydroxybenzophenone group, an unsubstituted or substitutedtriazine group, an unsubstituted or substituted salicylate group, anunsubstituted or substituted cyanoacrylate group, an unsubstituted orsubstituted oxanilide group, an unsubstituted or substitutedhydroxyphenyltriazine group, an unsubstituted or substitutedhydroxyphenylbenzotriazol group, or an unsubstituted or substitutedhydroxyphenylbenzophenone group).

Specifically, R^(x) is an unsubstituted or substituted C₁ to C₂₀alkylene group or an unsubstituted or substituted C₁ to C₂₀ alkyleneoxygroup. M may be oxygen (O) or —OCONH—. R^(y) may be an unsubstituted orsubstituted hydroxybenzophenone group or an unsubstituted or substitutedhydroxyphenyltriazine group. More specifically, R^(y) may be a2-hydroxybenzophenone group, a 2,4-dihydroxybenzophenone group, a2,2′-dihydroxybenzophenone group, a 2-hydroxy-4-methoxybenzophenonegroup, a 2-hydroxy-4-methoxy-4′-methylbenzophenone group, a2,2′-dihydroxy-4-methoxybenzophenone group, a2,4,4′-trihydroxybenzophenone group, a2,2′,4,4′-tetrahydroxybenzophenone group, a2,3,4,4′-tetrahydroxybenzophenone group, a2,3′4,4′-tetrahydroxybenzophenone group, or a2,2′-dihydroxy-4,4′-dimethoxybenzophenone group, or a group representedby Chemical Formula 3-1:

(wherein Chemical Formula 3-1, * is a linking site).R³ and R⁴ can provide crosslinkability and flexibility to thecomposition for window films. Specifically, R³ may be an unsubstitutedor substituted C₁ to C₂₀ alkyl group and R₄ may be a crosslinkablefunctional group. R³ and R⁴ can further improve hardness of a windowfilm by further improving crosslinkability of the composition for windowfilms. More specifically, R³ and R⁴ are each independently a(3,4-epoxycyclohexyl)methyl group, a (3,4-epoxycyclohexyl)ethyl group, a(3,4-epoxycyclohexyl)propyl group, a glycidoxy propyl group, a methylgroup, an ethyl group, an n-propyl group, or an isopropyl group.

Specifically, the siloxane resin comprising the compound represented byChemical Formula 1 may include at least one of Chemical Formulae 1-1 to1-13, without being limited thereto:

(EcSiO_(3/2))_(x)(RaSiO_(3/2))_(y)  <Chemical Formula 1-1>

(ECSiO_(3/2))_(x)(RbSiO_(3/2))_(y)  <Chemical Formula 1-2>

(EcSiO_(3/2))_(x)(RcSiO_(3/2))_(y)  <Chemical Formula 1-3>

(EcSiO_(3/2))_(x)(RdSiO_(3/2))_(y)  <Chemical Formula 1-4>

(GpSiO_(3/2))_(x)(RaSiO_(3/2))_(y)  <Chemical Formula 1-5>

(GpSiO_(3/2))_(x)(RbSiO_(3/2))_(y)  <Chemical Formula 1-6>

(GpSiO_(3/2))_(x)(RcSiO_(3/2))_(y)  <Chemical Formula 1-7>

(GpSiO_(3/2))_(x)(RdSiO_(3/2))_(y)  <Chemical Formula 1-8>

(OpSiO_(3/2))_(x)(RaSiO_(3/2))_(y)  <Chemical Formula 1-9>

(OpSiO_(3/2))_(x)(RbSiO_(3/2))_(y)  <Chemical Formula 1-10>

(OpSiO_(3/2))_(x)(RcSiO_(3/2))_(y)  <Chemical Formula 1-11>

(OpSiO_(3/2))_(x)(RdSiO_(3/2))_(y)  <Chemical Formula 1-12>

(in Chemical Formulae 1-1 to 1-12, Ra is represented by Chemical Formulai); Rb is represented by Chemical Formula ii); Rc is represented byChemical Formula iii); and Rd is represented by Chemical Formula iv),

(in Chemical Formulae i to iv, * is a linking site); and 0<x<1, 0<y<1,and x+y=1).

(EcSiO_(3/2))_(x1)(GpSiO_(3/2))_(x2)  <Chemical Formula 1-13>

(in Chemical Formula 1-13, 0<x1<1, 0<x2<1, and x1+x2=1).

Specifically, the siloxane resin comprising the compound represented byChemical Formula 2 may include at least one of compounds represented byChemical Formulae 2-1 to 2-36, without being limited thereto:

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-1>

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-2>

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-3>

(ECSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <Chemical Formula2-4>

(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <ChemicalFormula 2-5>

(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <ChemicalFormula 2-6>

(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <ChemicalFormula 2-7>

(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <ChemicalFormula 2-8>

(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-9>

(ECSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-10>

(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-11>

(ECSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <Chemical Formula2-12>

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-13>

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-14>

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-15>

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <Chemical Formula2-16>

(GpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <ChemicalFormula 2-17>

(GpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <ChemicalFormula 2-18>

(GpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <ChemicalFormula 2-19>

(GpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <ChemicalFormula 2-20>

(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-21>

(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-22>

(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-23>

(GpSiO3/2)x(GpMeSiO_(2/2))z(RdSiO_(3/2))y  <Chemical Formula 2-24>

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-25>

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-26>

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-27>

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <Chemical Formula2-28>

(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <ChemicalFormula 2-29>

(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <ChemicalFormula 2-30>

(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <ChemicalFormula 2-31>

(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <ChemicalFormula 2-32>

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RaSiO_(3/2))_(y)  <Chemical Formula2-33>

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RbSiO_(3/2))_(y)  <Chemical Formula2-34>

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RcSiO_(3/2))_(y)  <Chemical Formula2-35>

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(z)(RdSiO_(3/2))_(y)  <Chemical Formula2-36>

(in Chemical Formulae 2-1 to 2-36, Ra is represented by the ChemicalFormula i); Rb is represented by the Chemical Formula ii); Rc isrepresented by the Chemical Formula iii); Rd is represented by theChemical Formula iv); and 0<x<1, 0<y<1, 0<z<1, and x+y+z=1).

The siloxane resin comprising the compound represented by ChemicalFormula 1 or Chemical Formula 2 may have a weight average molecularweight of about 4,000 to about 100,000, specifically about 4,500 toabout 10,000, more specifically about 5,000 to about 7,000. Within thisrange, the siloxane resin can be easily produced and can provide goodproperties in terms of hardness and flexibility. The siloxane resincomprising the compound represented by Chemical Formula 1 or ChemicalFormula 2 may have a polydispersion index (PDI) of about 1.0 to 3.0,specifically about 1.5 to 2.5, and an epoxy equivalent weight of about0.1 mol/100 g to about 1.0 mol/100 g, specifically about 0.3 mol/100 gto about 0.7 mol/100 g. Within these ranges, the siloxane resin canprovide stable coating properties to the window film.

The crosslinking agent may contain a crosslinkable functional group toimprove hardness of the window film. The crosslinking agent may bepresent in an amount of about 10 parts by weight to about 30 parts byweight relative to 100 parts by weight of the siloxane resin or themixture thereof. Within this range, the composition can provide a windowfilm that can suppress curling and exhibits good hardness andflexibility.

Specifically, the crosslinking agent may include a non-cyclic aliphaticepoxy monomer, a cyclic aliphatic epoxy monomer, an aromatic epoxymonomer, a hydrogenated aromatic epoxy monomer, and an oxetane monomer.These crosslinking agents may be used alone or as a mixture thereof.

When the crosslinking agent comprises an epoxy monomer, the crosslinkingagent may have an epoxy equivalent weight of about 0.5 mol/100 g toabout 1.0 mol/100 g. Within this range, the composition can improveflexibility and hardness of the coating layer. The crosslinking agentmay have a weight average molecular weight of about 200 g/mol to about400 g/mol. Within this range, the composition can improve flexibilityand hardness of the coating layer.

The non-cyclic aliphatic epoxy monomer may include 1,4-butanedioldiglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentylglycoldiglycidyl ether, trimethylolpropane triglycidyl ether, polyethyleneglycol diglycidyl ether, glycerin triglycidyl ether, and polypropyleneglycol diglycidyl ether; polyglycidyl ethers of polyetherpolyol obtainedby adding one or more types of alkylene oxide to aliphatic polyhydricalcohols, such as ethylene glycol, propylene glycol, glycerin, and thelike; diglycidyl esters of aliphatic long-chain dibasic acids;monoglycidyl ethers of higher aliphatic alcohol; glycidyl ethers ofhigher fatty acids; epoxylated soybean oil; epoxy stearic acid butyl;epoxy stearic acid octyl; epoxylated linseed oil; epoxylatedpolybutadiene, and the like.

The cyclic aliphatic epoxy monomer is a compound having at least oneepoxy group in an alicyclic group, and may include alicyclic epoxycarboxylate or alicyclic epoxy (meth)acrylate. Specifically, the cyclicaliphatic epoxy monomer may include(3,4-epoxycyclohexyl)methyl-3′,4′-epoxycyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl-3′,4′-epoxy-6′-methylcyclohexanecarboxylate,diglycidyl 1,2-cyclohexanedicarboxylate,bis(3,4-epoxycyclohexylmethyl)adipate,bis((3,4-epoxy-6-methylcyclohexyl)methyl)adipate, ε-caprolactonemodified 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate,1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexanecarboxylate),3,4-epoxycyclohexylmethyl(meth)acrylate,epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metha-dioxane,trimethylcaprolactone modified3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate,β-methyl-δ-valerolactone modified3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate, ethyleneglycol di(3,4-epoxycyclohexylmethyl)ether, ethylenebis(3,4-epoxycyclohexanecarboxylate), 4-vinylcyclohexen dioxide,vinylcyclohexen monoxide, bis(3,4-epoxycyclohexylmethyl)malonate,bis(3,4-epoxycyclohexylmethyl)succinate,bis(3,4-epoxycyclohexylmethyl)glutarate,bis(3,4-epoxycyclohexylmethyl)pimelate,bis(3,4-epoxycyclohexylmethyl)azelate,bis(3,4-epoxycyclohexylmethyl)sebacate, and the like.

The aromatic epoxy monomer may include bisphenol type epoxy resins suchas diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, anddiglycidyl ether of bisphenol S; novolac type epoxy resins such as aphenol novolac epoxy resin, a cresol novolac epoxy resin, and ahydroxybenzaldehyde phenol novolac epoxy resin; and polyfunctional epoxyresins such as glycidyl ether of tetrahydroxyphenyl methane, glycidylether of tetrahydroxybenzophenone, and epoxylated polyvinyl phenol.

The hydrogenated aromatic epoxy monomer means a monomer obtained byselective hydrogenation of an aromatic epoxy monomer in the presence ofa catalyst under pressure. The aromatic epoxy monomer for thehydrogenated aromatic epoxy monomer may include the aromatic epoxymonomer described above.

The oxetane monomer may include at least one selected from among3-methyloxetane, 2-methyloxetane, 2-ethylhexyloxetane, 3-oxetanol,2-methyleneoxetane, 3,3-oxetanedimethanethiol,4-(3-methyloxetan-3-yl)benzonitrile,N-(2,2-dimethylpropyl)-3-methyl-3-oxetanmethaneamine,N-(1,2-dimethylbutyl)-3-methyl-3-oxetanmethaneamine,(3-ethyloxetan-3-yl)methyl(meth)acrylate,4-[(3-ethyloxetan-3-Amethoxy]butan-1-ol, 3-ethyl-3-hydroxymethyloxetane,xylenebisoxetane, and3-[ethyl-3[[(3-ethyloxetane-3-yl]methoxy]methyl]oxetane, without beinglimited thereto.

The initiator can cure the siloxane resins and the crosslinking agentdescribed above. The initiator may include at least one of aphotocationic initiator and a photo-radical initiator. The initiatorsmay be used alone or as a mixture thereof.

As the photocationic initiator, any typical photocationic initiatorknown to those skilled in the art may be used. Specifically, thephotocationic initiator may include an onium salt containing a cationand an anion. Specifically, examples of the cation may include:diaryliodonium such as diphenyliodonium, 4-methoxydiphenyliodonium,bis(4-methylphenyl)iodonium, bis(4-tert-butylphenyl)iodonium,bis(dodecylphenyl)iodonium, and(4-methylphenyl)[(4-(2-methylpropyl)phenyl)iodonium]; triarylsulfoniumsuch as triphenylsulfonium, diphenyl-4-thiophenylphenylsulfonium, anddiphenyl-4-thiophenoxyphenylsulfonium;bis[4-(diphenylsulfonio)phenyl]sulfide, and the like. Specifically,examples of the anion may include hexafluorophosphate (PF₆ ⁻),tetrafluoroborate (BF₄ ⁻), hexafluoroantimonate (SbF₆ ⁻),hexafluoroarsenate (AsF₆ ⁻), hexachloroantimonate (SbCl₆ ⁻), and thelike.

As the photo-radical initiator, any photo-radical initiator known tothose skilled in the art may be used. Specifically, the photo-radicalinitiator may include at least one of thioxanthone based, phosphorusbased, triazine based, acetophenone based, benzophenone based, benzoinbased, and oxime based photo-radical initiator.

The initiator may be present in an amount of about 0.01 parts by weightto about 20 parts by weight, specifically about 1 part by weight toabout 10 parts by weight, relative to 100 parts by weight of thesiloxane resin or the mixture thereof. Within this range, the siloxaneresin can be sufficiently cured without deterioration in transparency ofthe window film due to the remaining initiator.

The composition for window films according to this embodiment mayfurther include nanoparticles. The nanoparticles can further improvehardness of the window film. The nanoparticles may include at least oneof silica, aluminum oxide, zirconium oxide, and titanium oxide, withoutbeing limited thereto. The nanoparticles may also be subjected tosurface treatment with a silicone compound for mixing with the siloxaneresin. The nanoparticles are not limited to a particular shape or size.Specifically, the nanoparticles may include spherical, flake, oramorphous particles. The nanoparticles may have an average particle sizeof about 1 nm to about 200 nm, specifically about 10 nm to about 50 nm.Within this range, the nanoparticles can increase hardness of the windowfilm without affecting surface roughness and transparency of the windowfilm. The nanoparticles may be present in an amount of about 0.1 partsby weight to about 60 parts by weight, specifically about 10 parts byweight to about 50 parts by weight, relative to 100 parts by weight ofthe siloxane resins or the mixture thereof. Within this range, thenanoparticles can increase hardness of the window film without affectingsurface roughness and transparency thereof.

The composition for window films according to this embodiment mayfurther include additives. The additives can provide additionalfunctions to the window film. The additives may be any additivescommonly used for window films in the related art. Specifically, theadditives may include at least one of a UV absorbent, a reactioninhibitor, an adhesion promoter, a thixotropic agent, a conductivityimparting agent, a color adjusting agent, a stabilizer, an antistaticagent, an antioxidant, and a leveling agent, without being limitedthereto. The reaction inhibitor may include ethynylcyclohexane, theadhesion promoter may be an epoxy or alkoxysilyl group-containing silanecompound, and the thixotropic agent may be fumed silica. Theconductivity imparting agent may include metal powder such as silverpowder, copper powder, aluminum powder, and the like, and the coloradjusting agent may include pigments, dyes, and the like. The UVabsorbent can improve light resistant reliability of the window film.The UV absorbent may be any typical absorbent known to those skilled inthe art. Specifically, the UV absorbent may include at least one oftriazine based, benzimidazole based, benzophenone based, benzotriazolebased, and hydroxyphenyltriazine based UV absorbents, without beinglimited thereto. The additives may be present in an amount of about 0.01parts by weight to about 5 parts by weight, specifically about 0.1 partsby weight to about 2.5 parts by weight, relative to 100 parts by weightof the siloxane resins or the mixture thereof. Within this range, theadditives can improve hardness and flexibility of the window film whilerealizing effects thereof.

The composition for window films according to this embodiment mayfurther include a solvent to improve coatability, wettability orprocessability. The solvent may include methylethylketone,methylisobutylketone, and propylene glycol monomethyletheracetate,without being limited thereto.

The composition for window films according to this embodiment may have aviscosity of about 50 cP to about 2,000 cP at 25° C. Within this range,the composition allows easy formation of the window film.

Next, a method of preparing the siloxane resin comprising the compoundrepresented by Chemical Formula 1 will be described in detail.

The siloxane resin comprising the compound represented by ChemicalFormula 1 may be prepared through hydrolysis and condensation of a firstsilicon monomer only or a monomer mixture including the first siliconmonomer and a second silicon monomer. In one embodiment, the firstsilicon monomer may be present in an amount of about 20 mol % to about99.9 mol %, specifically about 20 mol % to about 99 mol %, morespecifically about 80 mol % to about 99 mol % in the monomer mixture.The second silicon monomer may be present in an amount of about 0.1 mol% to about 80 mol %, specifically about 1 mol % to about 80 mol %, morespecifically about 1 mol % to about 20 mol % in the monomer mixture. Inanother embodiment, one of the first silicon monomers may be preset inan amount of about 70 mol % to less than about 100 mol %, about 80 mol %to less than about 100 mol %, about 85 mol % to about 99 mol %, and theother one of the first silicon monomers may be present in an amount ofmore than about 0 mol % to about 30 mol %, more than about 0 mol % to 20mol %, or about 1 mol % to 15 mol %. Within these ranges, the first andsecond silicon monomers can improve hardness and light resistantreliability of the window film.

The first silicon monomer may include a silane compound represented byChemical Formula 4 and the second silicon monomer may include a silanecompound represented by Chemical Formula 5. These may be used alone orin combination thereof:

(wherein Chemical Formula 4, R¹ is the same as defined in ChemicalFormula 1, and R⁵, R⁶ and R⁷ are each independently a halogen, ahydroxyl group or a C₁ to C₁₀ alkoxy group).

(wherein Chemical Formula 5, R² is the same as defined in ChemicalFormula 1, and R⁸, R⁹ and R¹⁰ are each independently a halogen, ahydroxyl group or a C₁ to C₁₀ alkoxy group).

Specifically, the first silicon monomer may include at least oneselected from 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane,3-oxetanylmethyltrimethoxysilane, 3-oxetanylethyltrimethoxysilane,3-oxetanylpropyltrimethoxysilane, and 3-oxetanyloxytrimethoxysilane,without being limited thereto.

In one embodiment, the second silicon monomer may be prepared throughreaction of benzophenone having two or more hydroxyl groups with analkoxysilane. Specifically, the benzophenone having two or more hydroxylgroups may be 2,2′-dihydroxybenzophenone, 2,4-dihydroxybenzophenone,2,2′-dihydroxy-4-methoxybenzophenone,2,2′-dihydroxy-4-methoxy-4′-methylbenzophenone,2,2′-dihydroxy-4-methoxybenzophenone, 2,4,4′-trihydroxybenzophenone,2,2′,4,4′-tetrahydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone,2,3′4,4′-tetrahydroxybenzophenone, or2,2′-dihydroxy-4,4′-dimethoxybenzophenone. The alkoxysilane may includean alkoxysilane compound having one to three C₁ to C₅ alkoxy groups. Thebenzophenone having two or more hydroxyl groups and the alkoxysilane maybe reacted in a mole ratio of 1:1 to 1:1.5. A platinum catalyst may beused in order to improve reaction efficiency. In another embodiment, thesecond silicon monomer may be prepared by reacting a UV absorbent knownto those skilled in the art with an alkoxysilane compound having afunctional group capable of reacting with the UV absorbent.Specifically, the UV absorbent may include hydroxyphenyltriazine basedUV absorbents such as Tinuvin 400, Tinuvin 405, Tinuvin 460, and Tinuvin479; hydroxyphenyl benzotriazol based UV absorbents such as Tinuvin 99,Tinuvin 99-2, Tinuvin 171, Tinuvin 328, Tinuvin 384-2, Tinuvin 900,Tinuvin 928, Tinuvin 1130, Tinuvin 5050, Tinuvin 5060, Tinuvin 5151, andTinuvin P; benzophenone based UV absorbents such as Chimassorb 81 andChimassorb 90, without being limited thereto. Specifically, thealkoxysilane compound may include trialkoxysilane having an isocyanategroup. More specifically, the trialkoxysilane may contain an isocyanategroup-containing C₁ to C₁₀ alkyl group and C₁ to C₁₀ alkoxy group. Forexample, the trialkoxysilane may be 3-(triethoxysilyl)propylisocyanate.Reaction between the UV absorbent and trialkoxysilane may be performedin a solvent at about 20° C. to about 80° C. for about 1 hour to about12 hours. The solvent may be an organic solvent such as tetrahydrofuran.In reaction of the UV absorbent with trialkoxysilane, a catalyst may beused in order to improve reaction yield and may include a tin-basedcatalyst such as dibutyltin dilaurate. In another embodiment, the secondsilicon monomer may be obtained from commercially available products.For example, the second silicon monomer may include2-hydroxy-4-(3-triethoxysilylpropoxy)diphenylketone, without beinglimited thereto.

Hydrolysis and condensation of the monomer mixture may be performed by atypical method for preparation of a siloxane resin. Hydrolysis mayinclude reacting the first silicon monomer only or a mixture of thefirst silicon monomer and the second silicon monomer in a mixture ofwater and at least one of an acid and a base. Specifically, the acid maybe a strong acid such as HCl and HNO₃ and the base may be a strong basesuch as NaOH and KOH. Hydrolysis may be performed at about 20° C. toabout 100° C. for about 10 minutes to about 7 hours. Under theseconditions, hydrolysis efficiency of the silicon monomers can beimproved. Condensation may be performed at about 20° C. to about 100° C.for about 10 minutes to about 12 hours under the same conditions ashydrolysis. Under these conditions, hydrolysis efficiency of the siliconmonomers can be improved. A platinum catalyst may be further used inorder to improve efficiency in hydrolysis and condensation. The platinumcatalyst may include a vinylalkylsilane platinum complex including aKarstedt catalyst, platinum black, chloroplatinic acid, a chloroplatinicacid-olefin complex, a chloroplatinic acid-alcohol complex, or a mixturethereof.

Next, a method of preparing the siloxane resin comprising the compoundrepresented by Chemical Formula 2 will be described in detail.

The siloxane resin comprising the compound represented by ChemicalFormula 2 may be prepared through hydrolysis and condensation of amonomer mixture including a first silicon monomer, a second siliconmonomer, and a third silicon monomer. In the monomer mixture, the firstsilicon monomer may be present in an amount of about 40 mol % to about99 mol %, specifically about 80 mol % to about 98 mol %. In the monomermixture, the second silicon monomer may be present in an amount of about0.1 mol % to about 20 mol %, specifically about 0.1 mol % to about 10mol %, more specifically about 1 mol % to about 10 mol %. In the monomermixture, the third silicon monomer may be present in an amount of about0.1 mol % to about 40 mol %, specifically about 0.5 mol % to about 10mol %, more specifically about 1 mol % to about 10 mol %. Within theseranges, the first to third silicon monomers can improve hardness,flexibility and light resistant reliability of the window film.

The first silicon monomer may include a silane compound represented byChemical Formula 4, the second silicon monomer may include a silanecompound represented by Chemical Formula 5, and the third siliconmonomer may include a silane compound represented by Chemical Formula 6.These may be used alone or in combination thereof.

(wherein Chemical Formula 6, R³ and R⁴ are the same as defined inChemical Formula 2, and R¹¹ and R¹² are each independently a halogen, ahydroxyl group or a C₁ to C₁₀ alkoxy group).Specifically, the third silicon monomer may include at least oneselected from among 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane,dimethyldimethoxysilane, (3-glycidoxypropyl)methyldiethoxysilane, andethylmethyldiethoxysilane, without being limited thereto.

Next, a flexible window film according to one embodiment will bedescribed with reference to FIG. 1. FIG. 1 is a cross-sectional view ofa flexible window film according to one embodiment of the invention.

Referring to FIG. 1, a flexible window film (100) according to oneembodiment of the invention may include a base layer (110) and a coatinglayer (120), in which the coating layer (120) may be formed of thecomposition for window films according to the embodiment of the presentinvention.

The flexible window film (100) may have a curling of about 1.0 mm orless. Within this range, the flexible window film suffers from lesscurling and can be used as a window film for flexible displays.

The flexible window film (100) may have a pencil hardness of about 7H orhigher, a radius of curvature of about 5.0 mm or less, and a ΔY.I. ofabout 5.0 or less. Within this range, the flexible window film exhibitsgood properties in terms of hardness, flexibility and light resistantreliability and can be used as a window film for flexible displays.Specifically, the flexible window film (100) may have a pencil hardnessof about 7H to 9H, a radius of curvature of about 0.1 mm to about 5.0mm, and a ΔY.I. of about 0.1 to about 5.0.

The base layer (110) can improve mechanical strength of the flexiblewindow film (100) by supporting the coating layer (120) of the flexiblewindow film (100). The base layer (110) may be attached to a displaypart, a touchscreen panel or a polarizing plate via an adhesive layer orthe like.

The base layer (110) may be formed of an optically transparent flexibleresin. For example, the resin may include polyester resins includingpolyethylene terephthalate, polyethylene naphthalate, polybutyleneterephthalate, polybutylene naphthalate, and the like, polycarbonateresins, polyimide resins, polystyrene resins, poly(meth)acrylate resinsincluding polymethylmethacrylate, and the like. These resins may be usedalone or as a mixture thereof.

The base layer (110) may have a thickness of about 10 μm to about 200μm, specifically about 20 μm to about 150 μm, more specifically about 50μm to about 100 μm. Within this range, the base layer can be used in theflexible window film.

The coating layer (120) may be formed on the base layer (110) to protectthe base layer (110), the display part, the touchscreen panel or thepolarizing plate, and has high flexibility and high hardness to be usedfor a flexible display.

The coating layer (120) may have a thickness of about 5 μm to about 100μm, specifically about 10 μm to about 80 μm. Within this range, thecoating layer can be used in the flexible window film.

Although not shown in FIG. 1, functional surface layers such as ananti-reflection layer, an anti-glare layer, and a hard coating layer maybe further formed on the other surface of the coating layer (120) toprovide additional functions. In addition, although not shown in FIG. 1,the coating layer (120) may be further formed on the other surface ofthe base layer (110).

The flexible window film (100) is optically transparent and may be usedin a transparent display. Specifically, the flexible window film (100)may have a transmittance of about 88% or more, specifically about 88% toabout 100%, in the visible range, specifically in a wavelength range of400 nm to 800 nm. Within this range, the flexible window film can beused as a window film for flexible displays.

The flexible window film (100) may have a thickness of about 50 μm toabout 300 μm. Within this range, the flexible window film can be used asa window film for flexible displays.

The flexible window film (100) may be formed by coating and curing thecomposition for window films according to the embodiments on the baselayer (110).

A method of coating the composition for window films onto the base layer(110) is not particularly limited. For example, the composition forwindow films may be coated onto the base layer by bar coating, spincoating, dip coating, roll coating, flow coating, or die coating. Thecomposition for window films may be coated to a thickness of about 5 μmto about 100 μm on the base layer (110). Within this thickness range, adesired coating layer can be secured while providing good hardness,flexibility and reliability.

Curing is performed to form the coating layer by curing the compositionfor window films, and may include at least one of photocuring and heatcuring. Photocuring may include irradiating the coated composition at adose of about 10 mJ/cm² to about 1,000 mJ/cm² at a wavelength of 400 nmor less. Heat curing may be performed at a temperature of about 40° C.to about 200° C. for about 1 hour to about 30 hours. Under theseconditions, the composition for window films can be sufficiently cured.For example, heat curing may be performed after photocuring in order toachieve higher hardness of the coating layer.

Before curing the composition for window films coated onto the baselayer (110), the method may further include drying the composition. Whencuring is performed after drying, it is possible to prevent increase insurface roughness of the coating layer due to photocuring or heat curingfor a long period of time. Drying may be performed at about 40° C. toabout 200° C. for about 1 minute to about 30 hours, without beinglimited thereto.

Next, a flexible window film according to another embodiment will bedescribed with reference to FIG. 2. FIG. 2 is a cross-sectional view ofa flexible window film according to another embodiment of the invention.

Referring to FIG. 2, a flexible window film (200) according to anotherembodiment of the invention may include a base layer (110), a coatinglayer (120) formed on one surface of the base layer (110), and anadhesive layer (130) formed on the other surface of the base layer(110), in which the coating layer (120) may be formed of the compositionfor window films according to the embodiment of the present invention.

The flexible window film (200) may have a curling of about 1.0 mm orless, a pencil hardness of about 7H or higher, a radius of curvature ofabout 5.0 mm or less, and a ΔY.I. of about 5.0 or less. Within thisrange, the flexible window film exhibits good properties in terms ofhardness, flexibility and light resistant reliability and can be used asa window film for flexible displays.

The adhesive layer (130) formed on the other surface of the base layer(110) can facilitate adhesion between the flexible window film and atouchscreen panel, a polarizing plate or a display part. The flexiblewindow film according to this embodiment is substantially the same asthe flexible window film according to the above embodiment excluding theadhesive layer. Thus, the following description will be given of theadhesive layer alone.

The adhesive layer (130) attaches a polarizing plate, a touchscreenpanel, or a display part to the flexible window film (200) to bedisposed under the flexible window film (200), and may be formed of anadhesive composition for the adhesive layer. Specifically, the adhesivelayer (130) may be formed of an adhesive composition comprising anadhesive resin such as a (meth)acrylic resin, a urethane resin, asilicone resin, and an epoxy resin, a curing agent, a photoinitiator,and a silane coupling agent.

The (meth)acrylic resin is a (meth)acrylic copolymer having an alkylgroup, a hydroxyl group, an aromatic group, a carboxylic acid group, analicyclic group, a hetero-alicyclic group, and the like, and may includea typical (meth)acrylic copolymer. Specifically, the (meth)acrylic resinmay be formed of a monomer mixture including at least one of a(meth)acrylic monomer containing a C₁ to C₁₀ unsubstituted alkyl group,a (meth)acrylic monomer containing a C₁ to C₁₀ alkyl group having atleast one hydroxyl group, a (meth)acrylic monomer containing a C₆ to C₂₀aromatic group, a (meth)acrylic monomer containing a carboxylic acidgroup, a (meth)acrylic monomer containing a C₃ to C₂₀ alicyclic group,and a (meth)acrylic monomer containing a C₃ to C₁₀ hetero-alicyclicgroup having at least one of nitrogen (N), oxygen (O), and sulfur (S).

The curing agent is a polyfunctional (meth)acrylate and may include abifunctional (meth)acrylate such as hexanediol diacrylate; atrifunctional (meth)acrylate such as trimethylolpropanetri(meth)acrylate; a tetra-functional (meth)acrylate such aspentaerythritol tetra(meth)acrylate; a penta-functional (meth)acrylatesuch as dipentaerythritol penta(meth)acrylate; and a hexa-functional(meth)acrylate such as dipentaerythritol hexa(meth)acrylate, withoutbeing limited thereto.

The photoinitiator is a typical photoinitiator and may include thephoto-radical initiator described above.

The silane coupling agent may include an epoxy group-containing silanecoupling agent such as 3-glycidoxypropyltrimethoxysialne.

The adhesive composition may include 100 parts by weight of the(meth)acrylic resin, about 0.1 parts by weight to about 30 parts byweight of the curing agent, about 0.1 parts by weight to about 10 partsby weight of the photoinitiator, and about 0.1 parts by weight to about20 parts by weight of the silane coupling agent. With this composition,the adhesive layer formed of the adhesive composition allows theflexible window film to be sufficiently attached to the display part,the touchscreen panel, or the polarizing plate.

The adhesive layer (130) may have a thickness of about 10 μm to about100 μm. Within this range, the adhesive layer can sufficiently attachthe flexible window film to an optical device such as a polarizingplate.

Next, a flexible display according to one embodiment will be describedwith reference to FIG. 3 and FIG. 4. FIG. 3 is a cross-sectional view ofa flexible display according to one embodiment of the present inventionand FIG. 4 is a cross-sectional view of one embodiment of a display partshown in FIG. 3.

Referring to FIG. 3, a flexible display (300) according to oneembodiment of the invention includes a display part (350 a), an adhesivelayer (360), a polarizing plate (370), a touchscreen panel (380), and aflexible window film (390), which may include the flexible window filmaccording to the embodiments of the invention.

The display part (350 a) serves to drive the flexible display (300) andmay include a substrate and an optical device formed on the substrateand including an OLED, an LED or an LCD device. FIG. 4 is across-sectional view of one embodiment of the display part shown in FIG.3. Referring to FIG. 4, the display part (350 a) includes a lowersubstrate (310), a thin film transistor (316), an organic light emittingdiode (315), a flattening layer (314), a protective layer (318), and aninsulating layer (317).

The lower substrate (310) supports the display part (350 a), and thethin film transistor (316) and the organic light emitting diode (315)may be formed on the lower substrate (310). The lower substrate (310)may be formed with a flexible printed circuit board (FPCB) for drivingthe touchscreen panel (380). The flexible printed circuit board mayfurther include a timing controller, a power source, and the like inorder to drive an array of organic light emitting diodes.

The lower substrate (310) may include a substrate formed of a flexibleresin. Specifically, the lower substrate (310) may include a flexiblesubstrate such as a silicone substrate, a polyimide substrate, apolycarbonate substrate, and a polyacrylate substrate, without beinglimited thereto.

In a display area of the lower substrate (310), plural pixel domains aredefined by plural driving wires (not shown) and plural sensor wires (notshown) intersecting each other and each of the pixel domains may beformed with an array of organic light emitting diodes, each of whichincludes the thin film transistor (316) and the organic light emittingdiode (315) connected to the thin film transistor (316). In anon-display area of the lower substrate, a gate driver applying electricsignals to the driving wires may be formed in the form of a gate-inpanel. The gate-in panel circuit may be formed at one or both sides ofthe display area.

The thin film transistor (316) controls electric current flowing througha semiconductor by application of an electric field perpendicular to theelectric current and may be formed on the lower substrate (310). Thethin film transistor (316) may include a gate electrode (310 a), a gateinsulation layer (311), a semiconductor layer (312), a source electrode(313 a), and a drain electrode (313 b). The thin film transistor (316)may be an oxide thin film transistor which uses an oxide such as indiumgallium zinc oxide (IGZO), ZnO, or TiO as the semiconductor layer, anorganic thin film transistor which uses an organic material as thesemiconductor layer (312), an amorphous silicon thin film transistorwhich uses amorphous silicon as the semiconductor layer, or apolycrystalline silicon thin film transistor which uses polycrystallinesilicon as the semiconductor layer.

The flattening layer (314) covers the thin film transistor (316) and acircuit section (310 b) to flatten upper surfaces of the thin filmtransistor (316) and the circuit section (310 b) such that the organiclight emitting diode (315) can be formed thereon. The flattening layer(314) may be formed of a spin-on-glass (SOG) film, a polyimide polymer,or a polyacrylic polymer, without being limited thereto.

The organic light emitting diode (315) realizes a display throughself-emission, and may include a first electrode (315 a), an organiclight-emitting layer (315 b), and a second electrode (315 c), which arestacked in the stated order. Adjacent organic light emitting diodes maybe isolated from each other by the insulating layer (317). The organiclight emitting diode (315) may have a bottom emission type structurewherein light generated from the organic light-emitting layer (315 b) isemitted through the lower substrate, or a top-emission type structurewherein light from the organic light-emitting layer (315 b) is emittedthrough an upper substrate.

The protective layer (318) covers the organic light emitting diodes(315) to protect the organic light emitting diodes (315). The protectivelayer (318) may be formed of an inorganic material such as SiOx, SiNx,SiC, SiON, SiONC, and amorphous carbon (a-C), or an organic materialsuch as (meth)acrylates, epoxy polymers, imide polymers, and the like.Specifically, the protective layer (318) may include an encapsulationlayer in which an inorganic material layer and an organic material layerare sequentially stacked once or plural times.

Referring again to FIG. 3, the adhesive layer (360) serves to attach thedisplay part (350 a) to the polarizing plate (370), and may be formed ofan adhesive composition including a (meth)acrylate resin, a curingagent, an initiator, and a silane coupling agent.

The polarizing plate (370) can realize polarization of internal light orprevent reflection of external light to realize a display, or canincrease contrast of the display. The polarizing plate may be composedof a polarizer alone. Alternatively, the polarizing plate may include apolarizer and a protective film formed on one or both surfaces of thepolarizer. Alternatively, the polarizing plate may include a polarizerand a protective coating layer formed on one or both surfaces of thepolarizer. As the polarizer, the protective film and the protectivecoating layer, a typical polarizer, a typical protective film and atypical protective coating layer known in the art may be used.

The touchscreen panel (380) generates electrical signals throughdetection of variation in capacitance when a human body or a conductorsuch as a stylus touches the touchscreen panel, and the display part(350 a) may be driven by such electrical signals. The touchscreen panel(380) is formed by patterning a flexible conductor, and may includefirst sensor electrodes and second sensor electrodes each formed betweenthe first sensor electrodes and intersecting the first sensorelectrodes. The touchscreen panel (380) may include a conductivematerial such as metal nanowires, conductive polymers, and carbonnanotubes, without being limited thereto.

The flexible window film (390) may be disposed as an outermost layer ofthe flexible display (300) to protect the flexible display.

Although not shown in FIG. 3, adhesive layers may be further formedbetween the polarizing plate (370) and the touchscreen panel (380)and/or between the touchscreen panel (380) and the flexible window film(390) to reinforce coupling between the polarizing plate, thetouchscreen panel, and the flexible window film. The adhesive layers maybe formed of an adhesive composition including a (meth)acrylate resin, acuring agent, an initiator, and a silane coupling agent. Although notshown in FIG. 3, a polarizing plate may be disposed under the displaypart (350 a) to realize polarization of internal light.

Next, a flexible display according to another embodiment of the presentinvention will be described with reference to FIG. 5. FIG. 5 is across-sectional view of a flexible display according to anotherembodiment of the present invention.

Referring to FIG. 5, a flexible display (400) according to anotherembodiment of the invention includes a display part (350 a), atouchscreen panel (380), a polarizing plate (370), and a flexible windowfilm (390), which may include the flexible window film according to theembodiments of the invention. The flexible display according to thisembodiment is substantially the same as the flexible display accordingto the above embodiment except that the touchscreen panel (380) isdisposed under the polarizing plate (370) instead of being directlyformed on the flexible window film (390). In addition, the touchscreenpanel (380) may be formed together with the display part (350 a). Inthis case, since the touchscreen panel (380) is formed together with thedisplay part (350 a) on the display part (350 a), the flexible displayaccording to this embodiment is thinner and brighter than the flexibledisplay according to the above embodiment, thereby providing bettervisibility. In addition, the touchscreen panel (380) may be formed bydeposition, without being limited thereto. Although not shown in FIG. 5,adhesive layers may be further formed between the display part (350 a)and the touchscreen panel (380), between the touchscreen panel (380) andthe polarizing plate (370), and/or between the polarizing plate (370)and the flexible window film (390) to reinforce mechanical strength ofthe display. The adhesive layers may be formed of an adhesivecomposition including a (meth)acrylate resin, a curing agent, aninitiator, and a silane coupling agent. Although not shown in FIG. 5, apolarizing plate may be disposed under the display part (350 a) toprovide a good display image through polarization of internal light.

Next, a flexible display according to a further embodiment of thepresent invention will be described with reference to FIG. 6. FIG. 6 isa cross-sectional view of a flexible display according to a furtherembodiment of the present invention. Referring to FIG. 6, a flexibledisplay (500) according to a further embodiment of the inventionincludes a display part (350 b), an adhesive layer (360), and a flexiblewindow film (390), which may include the flexible window film accordingto the embodiments of the invention. The flexible display according tothis embodiment is substantially the same as the flexible displayaccording to the one embodiment except that the flexible display can bedriven by the display part (350 b) alone and the polarizing plate andthe touchscreen panel are omitted.

The display part (350 b) may include a substrate and an optical deviceformed on the substrate and including an OLED, an LED or an LCD device.The display part (350 b) may further include a touchscreen paneltherein.

Although the flexible window films according to the embodiments of theinvention are described as being applied to a flexible display, itshould be understood that the flexible window films according to theembodiments of the invention may also be applied to a non-flexibledisplay.

Hereinafter, the present invention will be described in more detail withreference to some examples. It should be understood that these examplesare provided for illustration only and are not to be construed in anyway as limiting the present invention.

Example 1

50 g of a monomer mixture comprising 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane and 5 mol % of2-hydroxy-4-(3-triethoxysilylpropoxy)diphenylketone was placed in a 200ml 2-neck flask. To the monomer mixture, 2 mol % of KOH and 1 mol % ofwater were added, followed by stirring at 65° C. for 4 hours. A siloxaneresin was prepared by removing remaining water and alcohol using avacuum distillation device, and methylethylketone was added thereto toobtain 90 wt % of the siloxane resin in terms of solid content. Thesiloxane resin had a weight average molecular weight of 6,200 asmeasured by gel permeation chromatography.

A composition for window films was prepared by mixing 100 parts byweight of the prepared siloxane resin, 10 parts by weight of acrosslinking agent CY-179 (Araldite), and 5 parts by weight of aninitiator CPI-100P (SAN-APRO). The prepared composition was coated ontoa polyethylene terephthalate film (TA043, Toyobo, thickness: 80 μm),followed by drying at 100° C. for 5 minutes, irradiation with UV lightat 1,000 mJ/cm², and heating at 80° C. for 4 hours, thereby preparing awindow film having a 50 μm thick coating layer.

Example 2

A window film was prepared in the same manner as in Example 1 exceptthat 10 parts by weight of bis(3,4-epoxycyclohexylmethyl)adipate(JIANGSU TETRA NEW MATERIAL TECHNOLOGY Co.) was used instead of 10 partsby weight of the crosslinking agent CY-179.

Example 3

A window film was prepared in the same manner as in Example 1 exceptthat 10 parts by weight of OXT-221(3-ethyl-3[[(3-ethyloxetane-3-yl)methoxy]methyl]oxetane, Toagosei) wasused instead of 10 parts by weight of the crosslinking agent CY-179.

Example 4

A window film was prepared in the same manner as in Example 1 exceptthat 20 parts by weight of bis(3,4-epoxycyclohexylmethyl)adipate(JIANGSU TETRA NEW MATERIAL TECHNOLOGY Co.) was used instead of 10 partsby weight of the crosslinking agent CY-179.

Example 5

A window film was prepared in the same manner as in Example 1 exceptthat 30 parts by weight of bis(3,4-epoxycyclohexylmethyl)adipate(JIANGSU TETRA NEW MATERIAL TECHNOLOGY Co.) was used instead of 10 partsby weight of the crosslinking agent CY-179.

Example 6 (1) Preparation of Second Silicon Monomer (Tinuvin 400-DerivedTriethoxysilane)

50.0 g of Tinuvin-400 (BASF) and 150 ml of toluene were mixed in a 1 Lround bottom flask. After washing the mixture three times with 150 ml ofdistilled water using a separatory funnel, an organic layer wascollected, followed by vacuum enrichment and drying. The obtainedconcentrate was dissolved in 85 ml of tetrahydrofuran, and 17.06 g of3-(triethoxysilyl)propylisocyanate and 1.0 g of a 5% tetrahydrofuransolution in which dibutyltin dilaurate was dissolved were further addedthereto. Reaction was performed by refluxing at 65° C. for 3 hours,followed by cooling to room temperature, and completion of the reactionwas confirmed through NMR. The obtained solution was completely driedthrough vacuum enrichment, thereby obtaining Tinuvin 400-derivedtriethoxysilane, which is a solid phase mixture of a second siliconmonomer represented by Chemical Chemical Formula ii and a second siliconmonomer represented by Chemical Chemical Formula iii.

(2) Preparation of Window Film

50 g of a monomer mixture comprising 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich) and 5 mol %of the prepared Tinuvin 400-derived triethoxysilane was placed in a 200ml 2-neck flask. To the monomer mixture, 2 mol % of KOH and 1 mol % ofwater were added, followed by stirring at 65° C. for 4 hours. A siloxaneresin was prepared by removing remaining water and alcohol using avacuum distillation device, and methylethylketone was added thereto toobtain 90 wt % of the siloxane resin in terms of solid content. Thesiloxane resin had a weight average molecular weight of 6,200 asmeasured by gel permeation chromatography.

A composition for window films was prepared by mixing 100 parts byweight of the prepared siloxane resin, 20 parts by weight ofbis(3,4-epoxycyclohexylmethyl)adipate (JIANGSU TETRA NEW MATERIALTECHNOLOGY Co.), and 5 parts by weight of an initiator CPI-100P(SAN-APRO). A window film was prepared using the prepared siloxane resinin the same manner as in Example 1.

Example 7

A siloxane resin was prepared in the same manner as in Example 1 exceptthat a monomer mixture was prepared by mixing 98 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1 mol % of2-hydroxy-4-(3-triethoxysilylpropoxy)diphenylketone, and 1 mol % ofdimethyldimethoxysilane. A composition for window films was prepared bymixing 100 parts by weight of the prepared siloxane resin, 20 parts byweight of bis(3,4-epoxycyclohexylmethyl)adipate (JIANGSU TETRA NEWMATERIAL TECHNOLOGY Co.), and 5 parts by weight of an initiator CPI-100P(SAN-APRO). A window film was prepared using the prepared siloxane resinin the same manner as in Example 1.

Example 8

A siloxane resin was prepared in the same manner as in Example 1 exceptthat a monomer mixture was prepared by mixing 98 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1 mol % of2-hydroxy-4-(3-triethoxysilylpropoxy)diphenylketone, and 1 mol % of2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane. A composition forwindow films was prepared by mixing 100 parts by weight of the preparedsiloxane resin, 20 parts by weight ofbis(3,4-epoxycyclohexylmethyl)adipate (JIANGSU TETRA NEW MATERIALTECHNOLOGY Co.), and 5 parts by weight of an initiator CPI-100P(SAN-APRO). A window film was prepared using the prepared siloxane resinin the same manner as in Example 1.

Example 9

Tinuvin 400-derived triethoxysilane was prepared in the same manner asin Example 6. A siloxane resin was prepared in the same manner as inExample 1 except that a monomer mixture was prepared by mixing 98 mol %of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1 mol % of Tinuvin400-derived triethoxysilane, and 1 mol % of dimethyldimethoxysilane. Acomposition for window films was prepared by mixing 100 parts by weightof the prepared siloxane resin, a mixture of 10 parts by weight ofCY-179 (Araldite) and 10 parts by weight ofbis(3,4-epoxycyclohexylmethyl)adipate (JIANGSU TETRA NEW MATERIALTECHNOLOGY Co.) as a crosslinking agent, and 5 parts by weight of aninitiator CPI-100P (SAN-APRO). A window film was prepared using theprepared siloxane resin in the same manner as in Example 1.

Example 10

Tinuvin 400-derived triethoxysilane was prepared in the same manner asin Example 6. A siloxane resin was prepared in the same manner as inExample 1 except that a monomer mixture was prepared by mixing 98 mol %of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 1 mol % of Tinuvin400-derived triethoxysilane, and 1 mol % of2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane. A composition forwindow films was prepared by mixing 100 parts by weight of the preparedsiloxane resin, a mixture of 10 parts by weight ofbis(3,4-epoxycyclohexylmethyl)adipate (JIANGSU TETRA NEW MATERIALTECHNOLOGY Co.) and 10 parts by weight of OXT-221 (Toagosei) as acrosslinking agent, and 5 parts by weight of an initiator CPI-100P(SAN-APRO). A window film was prepared using the prepared siloxane resinin the same manner as in Example 1.

Example 11

400 g of a monomer mixture comprising 95 mol % of2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM-303, Shin-EtsuChemicals Co., Ltd.) and 5 mol % of (3-glycidoxypropyl)trimethoxysilane(KBM-403, Shin-Etsu Chemicals Co., Ltd.) was placed in a 1 L 3-neckflask. To the monomer mixture, 0.1 mol % of KOH based on the amount ofthe monomer mixture and 1 equivalent weight of water based on the totalamount of the silicon monomers were added, followed by stirring at 65°C. for 8 hours and washing with toluene. Then, a siloxane resinrepresented by (EcSiO_(3/2))_(0.95)(GpSiO_(3/2))_(0.05) (weight averagemolecular weight: 5,500 as measured by GPC) was prepared throughconcentration of the resulting material. A window film was preparedusing the prepared siloxane resin in the same manner as in Example 1.

Comparative Examples 1 to 6

Window films were prepared in the same manner as in Example 1 exceptthat the kind and mole ratio of silicon monomers in preparation of thesiloxane resin and the kind and content of the crosslinking agent werechanged, as listed in Table 2.

Details of the compositions for window films prepared in Examples andComparative Examples are shown in Tables 1 and 2. The window filmsprepared in Examples and Comparative Examples were evaluated as toProperties (1) to (4) and evaluation results are shown in Table 1 and 2.

1. Curling: Referring to FIG. 7, a window film (1) including an 80 μmthick base layer and a 50 μm thick coating layer was cut to a size oflength×width (10 cm×10 cm) and placed on a floor surface (2) such thatthe base layer contacted the floor surface (2). Then, the window filmwas left at 25° C. and at 50% relative humidity. Thereafter, a maximumheight (H) from the floor surface (2) to an edge of the window film (1)was measured and averaged.

2. Pencil hardness: Pencil hardness was measured on a coating layer of awindow film using a pencil hardness tester (Heidon) in accordance withJIS K5400. Pencil hardness was measured using pencils of 6B to 9H(Mitsubishi Co., Ltd.) under conditions of a pencil load of 1 kg on thecoating layer, a scratch angle of 45°, and a scratch speed of 60 mm/min. When the coating layer had one or more scratches after being tested5 times using a certain pencil, pencil hardness was measured again usinganother pencil having one-level lower pencil hardness than the previouspencil. A pencil hardness value allowing no scratch to be observed allfive times on the coating layer was taken as pencil hardness of thecoating layer.

3. Radius of curvature: A window film (length×width×thickness, 3 cm×15cm×130 μm, base layer thickness: 80 μm, coating layer thickness: 50 μm)was wound around a jig for measuring a radius of curvature (CFT-200R,COVOTECH Co., Ltd.), kept wound for 5 seconds or more, unwound, and thenobserved with the naked eye to determine whether the window film hadcracks. Here, a radius of curvature in a compressive direction wasmeasured by winding the window film around the jig such that the coatinglayer of the window film contacted the jig, and a radius of curvature ina tensile direction was measured by winding the window film around thejig such that the base layer of the window film contacted the jig. Theradius of curvature was determined as a minimum radius of a jig causingno cracks on the window film, as measured in the compression directionwhile gradually decreasing the diameters of jigs from a jig having themaximum diameter.

4. Light resistant reliability: A yellow index (Y1) was measured on awindow film under a D65 light source at 2° (angle between the windowfilm and the light source) using a colorimeter (CM3600D, KonicaMinolta). Then, a yellow index (Y2) was measured on the window film bythe same method after irradiating the window film at a peak wavelengthof 306 nm for 72 hours using a light resistance tester (CT-UVT, CoreTechnology Inc.). Light resistant reliability was determined based on adifference in yellow index (Y2−Y1, ΔY.I.) between before irradiation andafter irradiation.

TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 11 Silicon 2-(3,4- 95 95 95 95 9595 98 98 98 98 — monomer epoxycyclohexyl)ethyl (mol %) triethoxysilane2-hydroxy-4-(3- 5 5 5 5 5 — 1 1 — — —triethoxysilylpropoxy)diphenylketone Tinuvin 400- — — — — — 5 — — 1 1 —derived triethoxysilane Dimethyldimethoxysilane — — — — — — 1 — 1 — —2-(3,4- — — — — — — — 1 — 1 — epoxycyclohexyl)ethyl methyldiethoxysilane2-(3,4- — — — — — — — — — — 95 epoxycyclohexyl)ethyl trimethoxysilane(3- — — — — — — — — — — 5 glycidoxypropyl)trimethoxysilane CrosslinkingCY-179 10 — — — — — — — 10 — 10 agent bis[(3,4- — 10 — 20 30 20 20 20 1010 — (parts by epoxycyclohexyl)methyl]adipate weight) OXT-221 — — 10 — —— — — — 10 — Initiator (parts by weight) 5 5 5 5 5 5 5 5 5 5 5 Curling(mm) 0.9 0.8 1.0 0.6 0.3 0.6 0.5 0.4 0.8 0.9 0.3 Pencil hardness 7H 9H7H 8H 7H 7H 8H 8H 7H 7H 8H Radius of curvature (mm) 3.7 3.5 3.8 3.3 3.13.6 2.8 3.0 3.4 3.5 2.9 Light resistant reliability (ΔY.I.) 2.1 2.1 2.01.9 2.0 2.2 1.9 2.0 2.2 2.1 1.8

TABLE 2 Comparative Example 1 2 3 4 5 6 Silicon2-(3,4-epoxycyclohexyl)ethyl 95 95 98 98 95 95 monomer triethoxysilane(mol %) 2-hydroxy-4-(3- triethoxysilylpropoxy)diphenylketone 5 5 1 1 5 —Tinuvin 400-derived triethoxysilane — — — — — 5 Dimethyldimethoxysilane— — 1 — — — 2-(3,4- — — — 1 — —epoxycyclohexyl)ethylmethyldiethoxysilane Crosslinking CY-179 — — — — —— agent bis[(3,4-epoxycyclohexyl)methyl]adipate 5 35 5 35 — — (parts byOXT-221 — — — — — — weight) Initiator (parts by weight) 5 5 5 5 5 5Curling (mm) 23 0 17 0 37 34 Pencil hardness 9H 2H 8H H 6H 7H Radius ofcurvature (mm) 5.6 3.6 5.7 3.5 6.4 6.0 Light resistance (ΔY.I.) 2.4 2.12.3 2.2 1.8 1.6

As shown in Table 1, the flexible window films of Examples had a smallcurl of 1 mm or less of curling, a pencil hardness of 7H or more meaninghigh hardness, a radius of curvature of 5.0 mm or less of goodflexibility, and good light resistant reliability to be used as a windowfilm for flexible displays.

As shown in Table 2, the flexible window films of Comparative Examples 1to 4, in which the content of the crosslinking agent was not within therange of the present invention, had a high curl or exhibited poorproperties in terms of at least one of pencil hardness, radius ofcurvature and light resistant reliability. The flexible window films ofComparative Examples 5 and 6, which did not include the crosslinkingagent, exhibited poorer properties in terms of curling and radius ofcurvature.

It should be understood that various modifications, changes,alterations, and equivalent embodiments can be made by those skilled inthe art without departing from the spirit and scope of the invention.

1. A composition for window films, comprising: a siloxane resinrepresented by Chemical Formula 1 or a siloxane resin represented byChemical Formula 2 or a mixture thereof, a crosslinking agent, and aninitiator, wherein the crosslinking agent is present in an amount ofabout 10 parts by weight to about 30 parts by weight relative to 100parts by weight of the siloxane resin or the mixture thereof:(R¹SiO_(3/2))_(x)(R²SiO_(3/2))_(y)  <Chemical Formula 1> (whereinChemical Formula 1, R¹ is a crosslinkable functional group; R² is a UVabsorption functional group or a UV absorption functionalgroup-containing group; and 0<x≦1, 0≦y<1, and x+y=1),(R¹SiO_(3/2))_(x)(R³R⁴SiO_(2/2))_(z)(R²SiO_(3/2))_(y)  <Chemical Formula2> (wherein Chemical Formula 2, R¹ is a crosslinkable functional group;R² is a UV absorption functional group or a UV absorption functionalgroup-containing group; R³ and R⁴ are each independently hydrogen, acrosslinkable functional group, an unsubstituted or substituted C₁ toC₂₀ alkyl group, or an unsubstituted or substituted C₅ to C₂₀ cycloalkylgroup, at least one of R³ and R⁴ being an unsubstituted or substitutedC₁ to C₂₀ alkyl group; and 0<x<1, 0<y<1, 0<z<1, and x+y+z=1).
 2. Thecomposition for window films according to claim 1, wherein the siloxaneresin comprises a siloxane resin represented by Chemical Formula 1-13:(EcSiO_(3/2))_(x1)(GpSiO_(3/2))_(x2)  <Chemical Formula 1-13> (whereinChemical Formula 1-13, Ec is a (3,4-epoxycyclohexyl)ethyl group, Gp is a3-glycidoxy propyl group, and 0<x1<1, 0<x2<1, and x1+x2=1).
 3. Thecomposition for window films according to claim 1, wherein thecrosslinking agent comprises a cyclic aliphatic epoxy monomer.
 4. Thecomposition for window films according to claim 3, wherein the cyclicaliphatic epoxy monomer comprises at least one selected from(3,4-epoxycyclohexyl)methyl-3′,4′-epoxyyclohexanecarboxylate,3,4-epoxy-6-methylcyclohexylmethyl-3′,4′-epoxy-6′-methylyclohexanecarboxylate,bis(3,4-epoxycyclohexylmethyl)adipate,bis((3,4-epoxy-6-methylcyclohexyl)methyl)adipate,bis(3,4-epoxycyclohexylmethyl)malonate,bis(3,4-epoxycyclohexylmethyl)succinate,bis(3,4-epoxycyclohexylmethyl)glutarate,bis(3,4-epoxycyclohexylmethyl)pimelate,bis(3,4-epoxycyclohexylmethyl)azelate, andbis(3,4-epoxycyclohexylmethyl)sebacate.
 5. A flexible window filmcomprising a base layer and a coating layer formed on one surface of thebase layer, wherein the flexible window film has a curling of about 1.0mm or less and the coating layer is formed of the composition for windowfilms according to claim
 1. 6. The flexible window film according toclaim 5, further comprising: an adhesive layer formed on the othersurface of the base layer.
 7. A flexible display comprising the flexiblewindow film according to claim
 5. 8. The flexible display according toclaim 7, wherein the flexible display comprises a display part, anadhesive layer formed on the display part, a polarizing plate formed onthe adhesive layer, a touchscreen panel formed on the polarizing plate,and the flexible window film formed on the touchscreen panel.
 9. Theflexible display according to claim 7, wherein the flexible displaycomprises a display part, a touchscreen panel formed on the displaypart, a polarizing plate formed on the touchscreen panel, and theflexible window film formed on the polarizing plate.
 10. The flexibledisplay according to claim 7, wherein the flexible display comprises adisplay part, an adhesive layer formed on the display part, and theflexible window film formed on the adhesive layer.
 11. The flexibledisplay according to claim 10, wherein the display part furthercomprises a polarizing plate disposed at an upper or lower side thereof.